1. Field of Invention
This invention relates to tire molds and especially to the method of making mold segments of sintered powdered metal from tire model segments of a refractory material utilizing pressure vessels and heaters.
2. Description of the Related Art
In the manufacture of tires the composite rubber reinforced article is vulcanized under heat and pressure. During this operation, it is important that the gases and moisture be vented and not trapped in the tire where this may cause the tire to fail. It has been found that metal parts made from powdered metal have pores which have the capability of absorbing gases during a molding process. This property has been utilized in molding and casting by forming and compressing parts under pressure in various applications shown and described in U.S. Pat. No. 5,850,590. Also in U.S. Pat. No. 5,623,727 parts have been made by using a model or forging die on a moveable ram for shaping and forming a part from powdered metal. In U.S. Pat. No. 5,625,861 a process is disclosed for producing a porous metal body by shaping powdered metal in a capsule under pressure.
The object of this invention is to provide a segmental tire mold with porous molding surfaces to absorb gases and moisture during curing of a tire without the necessity of providing vents which may be filled with rubber and result in projecting fingers on the tire which need to be trimmed. The absorption of gases and moisture in the pores of the mold can also be provided in locations where it is difficult to provide vents.
In accordance with one aspect of the invention, there is provided a method of making a porous metal tread segment for a tire mold from metal powder comprising:
(a) forming a segmented tire mold model of refractory material;
(b) mounting the model in a milling machine;
(c) cutting a tread surface in the model;
(d) compacting the metal powder against a segment of the model to form the tread segment;
(e) heating the tread segment to sinter the metal powder; and
(f) machining the tread segment for mounting in a segmental tire mold mechanism.
Still other benefits and advantages of the invention will become apparent to those skilled in the art to which it pertains upon a reading and understanding of the following detailed specification.